Package com.oracle.deviceaccess.gpio

Interfaces and classes for reading and writing from/to GPIO (General Purpose Input Output) pins and ports of the device.

See: Description

Interface Summary

Interface	Description
GPIOPin	The GPIOPin interface provides methods for controlling a GPIO pin.
GPIOPort	The GPIOPort interface provides methods for controlling a GPIO port.
PinListener	The PinListener interface defines methods for getting notified of GPIO pin value changes.
PortListener	The PortListener interface defines methods for getting notified of GPIO port value changes.

Class Summary

Class	Description
GPIOPinConfig	The GPIOPinConfig class encapsulates the hardware addressing information, and static and dynamic configuration parameters of a GPIO pin.
GPIOPortConfig	The GPIOPortConfig class encapsulates the hardware addressing information, and static and dynamic configuration parameters of a GPIO port.
PinEvent	The PinEvent class encapsulates GPIO pin value changes.
PortEvent	The PortEvent class encapsulates GPIO port value changes.

Package com.oracle.deviceaccess.gpio Description

Interfaces and classes for reading and writing from/to GPIO (General Purpose Input Output) pins and ports of the device.

A GPIO port is a platform-defined grouping of GPIO pins that may be configured for output or input. Note that GPIO pins that are part of a GPIO port cannot be retrieved nor controlled individually as GPIOPin instances.

In order to use a specific pin or port, an application should first open and obtain and obtain a GPIOPin instance or GPIOPort instance, respectively, for the pin or port it wants to use using its numerical ID, name, type (interface) and/or properties:

• Using its ID

   GPIOPin pin = (GPIOPin) PeripheralManager.open(1);
   GPIOPort port = (GPIOPort) PeripheralManager.open(0);
   

• Using its name and interface

   GPIOPin pin = (GPIOPin) PeripheralManager.open("LED_PIN", GPIOPin.class, null);
   GPIOPort port = (GPIOPort) PeripheralManager.open("LCD_DATA_PORT", GPIOPort.class, null);
   

Once a pin opened, an application can obtain the current value of a GPIO pin by calling the GPIOPin.getValue() method and set its value by calling the GPIOPin.setValue(boolean) method.
Once a port opened, an application can obtain the current value of a GPIO port by calling the GPIOPort.getValue() method and set its value by calling the GPIOPort.setValue(int) method.

 pin.setValue(true);
 port.setValue(0xFF);
 

When done, the application should call the GPIOPin.close() or GPIOPort.close() method to release the pin or port, respectively.

 pin.close();
 port.close();
 

The following sample code gives an example of using the GPIO API. It shows how to control GPIO Pins. It registers a pin listener for the GPIO input pin a switch button is attached to. When the button is pressed the listener is notified to turn the LED on or off by setting accordingly the GPIO output pin the LED is attached to.

 GPIOPin switchPin = null;
 GPIOPin ledPin = null;
 try {
     switchPin = (GPIOPin) PeripheralManager.open(1);
     ledPin = (GPIOPin) PeripheralManager.open(3);
     switchPin.setInputListener(new PinListener() {
         public void valueChanged(PinEvent event) {
             try {
                 ((GPIOPin) event.getPeripheral()).setValue(event.getValue()); // turn LED on or off
             } catch (IOException ex) {
                 // Ignored
             } catch (PeripheralNotAvailableException ex) {
                 // Ignored
             }
         }
     });
 } catch (IOException ex) {
     // Handle exception
 } catch (PeripheralNotFoundException ex) {
     // Handle exception
 } catch (PeripheralNotAvailableException ex) {
     // Handle exception
 } finally {
     if (switchPin != null) {
         try {
             switchPin.close();
         } catch (IOException ex) {
         }
     }
     if (ledPin != null) {
         try {
             ledPin.close();
         } catch (IOException ex) {
         }
     }
 }
 

Note that the underlying platform configuration may allow for some GPIO pins or ports to be set by an application for either output or input while others may be used for input only or output only and that their direction can not be changed by an application. Note also that asynchronous notification of pin or port value changes is only loosely tied to hardware-level interrupt requests. The platform does not guarantee notification in a deterministic/timely manner.

Because of performance issue, procedures handling GPIO pins, and especially event listeners, should be implemented to be as fast as possible.

Security

GPIO pins and ports are opened by invoking one of the com.oracle.deviceaccess.PeripheralManager.open methods. The permissions below allow access to be granted to GPIO pins and ports as a whole as well as to to some of their protected functions.

Permission	Function
"com.oracle.deviceaccess.gpio"	Access to GPIO pins and ports (as a whole)
"com.oracle.deviceaccess.gpio.GPIOPin.setDirection"	Changing the direction of a GPIO pin
"com.oracle.deviceaccess.gpio.GPIOPort.setDirection"	Changing the direction of a GPIO port